互连光栅衍射模式的设计与研究:2.正弦型位相光栅

根据光栅互连在光计算及信息处理中应用的研究与发展,对正弦型位相光栅进行了结构设计,以便产生只含有0级和±1级,或只含有±1级的两种特殊的衍射模式,分别用于实现光学蝶互连或操纵器网络互连等。论文给出了详细的计算和实验结果。     

Design and analysis of low-reflection grating microstructures for a solar energy absorber

The problem of calculating the photo-induced current in an n⁺p junction solar cell with a microstructure grating on the top is formulated. For the case where useful absorption regions lie below the grating a closed solution of the problem is obtained, in which the carrier photo-generation rate is calculated using a full-vector electromagnetic simulation technique. Two structures: filled lamellae grating and overlayer, and filled V-groove grating and overlayer are considered. The first structure is optimized with respect to the integral photo-current and the second with respect to reflection loss. Both optimized structures are much less reflective and more efficient than an optimized flat-surface Si–SiO₂ layer cell.     

Evaluation of particle recovery from microalgae

Coccoliths are micro-structured biomineral particles found in cell protective covering layers of coccolithophore species. They are mainly composed of CaCO₃ and their individual crystal entities are arranged in such a way that they construct complex and unique structures. This complexity is found down to the individual particle level and appears to have promising properties to offer. This study focuses on the essential step prior to any kind of implementation, which is the recovery of the material. It summarizes cleaning protocols found in literature, compares them for the first time for the same freshly cultivated material and addresses challenges that still need to be overcome. Further, it highlight the advantages and disadvantages of the best cleaning protocols, suggests optimizations with promising results and uses size distribution measurements to analyse the recovery efficiency. To that end, further characterization techniques, new for coccoliths, are introduced and used to improve our current knowledge of the particles behaviour.     

Steel slag waste combined with melamine pyrophosphate as a flame retardant for rigid polyurethane foams

To explore the potential application of industrial waste, steel slag powder in combination with melamine pyrophosphate (MPP) was adopted to improve the flame retardancy of rigid polyurethane foam (RPUF). The incorporation of steel slag slightly reduced the thermal conductivity of the resulting flame-retardant RPUF samples. The addition of MPP and/or steel slag did not significantly alter the thermal stability in terms of T_-10% and T_max but did obviously increase the T_-50% value, suggesting the improved thermal resistance of the residues. The coaddition of MPP and steel slag into RPUF resulted in higher LOI values and lower peak heat release rates than the samples incorporating either MPP or steel slag alone. The superior flame retardancy could be attributed to MPP promoting char formation, which then acted as a barrier at the beginning of RPUF thermal decomposition; simultaneously, the thermally stable inorganics in the steel slag powder strengthened the thermal resistance of this char layer.     

Rotating light fields of an azimuthally polarized light beam generated by two-belt spiral phase modulation

The tightly focused light fields of an azimuthally polarized light beam through a two-belt spiral phase plate were investigated. The focused light fields are presented in accordance with vectorial diffraction theory. The results show that a rotating light field with different intensity patterns can be produced by altering the azimuthal polarization state and modulating the two-belt spiral phase. A concurrent change in spiral handedness in the two-belt phase plate causes the rotation to occur along the direction of propagation, and the relative angular offset in the two-belt spiral phase plate can be exploited to rotate the light fields. The proposed method is useful for engineering the intensity distribution near the focal plane and related applications.     

X射线粉末衍射仪智能辅助校正系统

X射线粉末衍射仪（X-Ray powder Diffraction,XRD）是物质研究的精密仪器,物理结构复杂,微小的硬件偏差会对衍射数据质量造成影响,对其硬件设备进行偏差校正将有效保证数据正确性,在校正偏差前需要进行偏差类型识别.通常衍射仪设备调校多由设备厂商专家使用专用仪器和设备逐项排查的方式进行偏差校正,对人员经验有较高依赖、调校过程复杂且效率低.为了提高偏差识别效率,本文探讨了X射线粉末衍射仪偏差类型及其产生原因,并开发了一套基于分类预测的X射线粉末衍射仪智能辅助校正系统.该系统采用通用计算机硬件平台,通过特征提取、模型训练等步骤分析标准样品衍射数据,自动化识别仪器状态、辅助校正.结果表明该系统可以快速识别偏差,达到辅助校正的目的.     

Nanoscale waveguiding methods

While 32 nm lithography technology is on the horizon for integrated circuit (IC) fabrication, matching the pace for miniaturization with optics has been hampered by the diffraction limit. However, development of nanoscale components and guiding methods is burgeoning through advances in fabrication techniques and materials processing. As waveguiding presents the fundamental issue and cornerstone for ultra-high density photonic ICs, we examine the current state of methods in the field. Namely, plasmonic, metal slot and negative dielectric based waveguides as well as a few sub-micrometer techniques such as nanoribbons, high-index contrast and photonic crystals waveguides are investigated in terms of construction, transmission, and limitations. Furthermore, we discuss in detail quantum dot (QD) arrays as a gain-enabled and flexible means to transmit energy through straight paths and sharp bends. Modeling, fabrication and test results are provided and show that the QD waveguide may be effective as an alternate means to transfer light on sub-diffraction dimensions.     

Frequency dependent directivity of periodic permanent magnet electromagnetic acoustic transducers

Beam steering has been achieved using shear horizontal waves generated using a periodic permanent magnet (PPM) electromagnetic transducer (EMAT). Unlike phased arrays, where steering is achieved by carefully controlling the firing of individual elements, the spatial periodicity of the PPM EMAT is ultilised to steer the beam whilst exciting all elements simultaneously. Due to the periodic nature of the array, the interference of individual waves from each of the elements creates a highly frequency dependent angle of propagation, allowing the directivity to be changed by simply varying the frequency of the input signal. Simultaneous excitation precludes the need for complicated and expensive phased array hardware. A frequency domain model is developed so that the beam characteristics, such as steering angle and beam width, can be calculated, allowing for investigation into the beam steering qualities of the PPM transducer. Broadband pulsed generation is also demonstrated, showing how a wave is generated over a large range of angles, meaning a large area can be covered with a single pulse. Interesting properties of this wave, such as a variation of frequency as a function of angle, and how this can be useful, are also discussed.     

共溅法形成钽金属硅化物出现Ta_5Si_3的研究

对polySi/SiO_2/Si结构上的共溅射 Ta +xSi 薄层未经退火处理在1000℃/30＇条件下进行直接湿氧氧化,经AES和X衍射检测分析,得知氧化后的结构为SiO_2/Ta_5Si_3/TaSi_2/PolySi/SiO_2/Si,其中,Ta_5Si_3相为四角晶系,晶格常数为:α_0= 6.516A,c_0=11.873A.Ta_5Si_3相的出现,对多层结构的稳定性及电导特性有不利影响.从实验证实在较高温度下氧化Ta_5Si_3不会出现,如在1100℃/30＇条件下进行直接湿氧氧化,检测结果表明没有Ta_5Si_3相.已经形成的Ta_5Si_3在适当条件下经热处理会消失.